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CHICAGO NATURAL HISTORY MUSEUM
Preserving Birds for Study
EMMET R. BLAKE
Associate Curator, Division of Birds
NATURAL HISTORY"
MUSEUM
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FIELDIANA: TECHNIQUE
NUMBER 7
Published by
CHICAGO NATURAL HISTORY MUSEUM
JULY 22, 1949
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Preserving Birds for Study
INTRODUCTION
Birdskins preserved in museum collections for study
purposes are the source of much that is known about birds
today. From them it is possible to solve various problems
of individual and geographical variation, of plumage dif-
ferences and changes due to age, season or sex. Many
details of classification and distribution can be determined
only by the methodical study and comparison of large se-
ries of preserved skins. Research collections of such
'study skins" are maintained wherever studies on the
classification and geographic distribution of birds are
carried on.
No single collection of birds contains all described
forms. To a far lesser degree do individual collections
have adequate series of duplicate specimens representing
the plumages of both sexes, at all seasons, from all parts
of their range. For this reason natural history museums
are continually in need of additional specimens to supple-
ment those already available. The traveler, whether ama-
teur naturalist, student or casual tourist, can often obtain
specimens that materially advance the frontiers of research.
The present manual is intended as a guide for those who
would prepare themselves for the task of preserving birds
collected for scientific purposes. The collector should re-
member that it is against the laws of the United States and
Canada to collect most birds without a specific Federal
and State permit. The beginner, however, may collect un-
protected birds like English sparrows, starlings, and crows,
or game birds in the "open season."
Good collecting depends in part upon thorough famili-
arity with the bird-life of the collecting area, knowledge of
the local and general status of each species, and recogni-
tion of its field characters as an aid in spot identification.
Even when these conditions are met, there is rarely time to
exploit a locality fully. Whenever a compromise must be
5
6 FIELDIANA: TECHNIQUE, NO. 7
made between the ideal and the practical, the following
principles should serve as a guide in collecting.
A representative collection is usually more desirable
than one containing large series of some species but lack-
ing in individuals of other species also occurring in the
area. Unless otherwise directed, make every effort to col-
lect the greatest possible variety of birds in each locality
before accumulating large series of duplicate specimens.
When the relative importance or local abundance of various
species is uncertain, it is best to limit your series to four
specimens of each until a good representation of the fauna
has been obtained. Thereafter, make every effort to obtain
larger series of each species; eight or ten specimens from
each locality are desirable, since present-day research is
often based upon statistical methods.
In each locality always collect the first specimen of
each species seen. The form may later prove to be abun-
dant and well-known but, even so, a locality record is
always valuable. Never delay in collecting this specimen,
even though the species seems to be locally abundant.
Too often the reverse is true and the opportunity may never
come again. Regardless of its condition, always preserve
the first specimen of each species seen as a record, at
least until more satisfactory specimens have been collected.
Large or strikingly colored birds of all sizes are gener-
ally better known than small or obscurely marked species.
If time for collecting is limited, give the latter first prior-
ity and collect the larger species as circumstances permit,
unless certain of these have been designated as particu-
larly desirable.
INSTRUMENTS AND MATERIALS
Few tools are essential; birdskins can be prepared with
a knife or scissors alone. Although an elaborate set of
taxidermy tools is not necessary, the following instruments
and materials aredesirable for competent general collecting.
1 surgeon's scalpel, small size.
1 surgeon's scalpel, medium size.
1 pair of surgical scissors, small, having one blade rounded at the end.
1 pair of surgical scissors, medium size, same as above.
1 pair of bone-cutters, or short shears.
BLAKE: PRESERVING BIRDS "
1 pair of forceps (5 in.), straight, with long slender tips.
1 pair of forceps (6-7 in.), straight, with blunt tips.
1 pair of forceps (10 in.), same as above.
1 pair of small pliers, with wire-cutting edge.
Annealed, galvanized wire (sizes 11, 16, 22).
1 small, stiff brush, for removing dried blood, etc.
1 small carborundum stone.
Sewing needles of assorted sizes.
Linen or cotton thread (Nos. 8, 36, 80).
Small cotton "grocery string," for binding the artificial bodies of very
large specimens.
Pins of nickeled brass.
1 metric rule and pair of dividers.
Wooden "spindles," assorted lengths (6, 8, 14 in.), smoothly tapered from
fine point to butt (1/4 - 3/8 in. in diameter).
Cotton batting or "quilting cotton," long-fibred and capable of being
shredded into long strips and thin sheets. One pound of this cotton is
sufficient for approximately sixty small to medium-sized birds.
Absorbent cotton.
Tow and/ or fine wood "excelsior," if large birds are to be collected. Dry
moss leaves or grass may be used if necessary.
Cheesecloth or mosquito-netting for wrapping large birds.
Corn meal.
Heavy .magnesium oxide or potato starch for drying wet feathers.
Grease solvent, preferably carbon tetrachloride. Benzine or naphthaline may
also be used, but they are less satisfactory in every respect.
Powdered arsenic or borax, used as a preservative on the flesh side of
every skin.
Powdered alum; useful in drying and hardening the skins of very large birds
in humid climates.
Naphthalene flakes; retard mold and are useful as an insect deterrent in the
field, or for safeguarding specimens in transit.
Formalin or alcohol (85 per cent) for preserving anatomical specimens.
Museum specimen labels, pens, and black, waterproof ink.
Field catalogue. A small, durable notebook having lined pages is desirable
for recording all data, and for the elaboration of general field
observations.
An adequate "spindle" can be trimmed from a straight stick as needed,
but it is desirable to prepare several that are smoothly planed, and of various
sizes, for regular use in the field.
Arsenic is used for the preservation of birdskins by most museums and
commercial taxidermists. Powdered borax is much less effective as an insect
deterrent but may be substituted for arsenic if necessary. If used, it must be
applied liberally to the fresh skin.
3 Small plastic bags that can be sealed under heat and pressure have been
suggested for shipping "wet specimens" after they have been properly pre-
served in formalin or alcohol.
8 FIELDIANA: TECHNIQUE, NO. 7
PRELIMINARY CARE OF SPECIMENS
Time will be saved at the skinning table and a better
specimen will result if the bird is properly attended as
soon as shot. It should be picked up by the beak or feet
(never by the tail) and the plumage examined for blood or
other foreign matter. Blood stains and mud are difficult to
remove when dry, but may be wiped from the feathers eas-
ily with absorbent cotton when fresh.
Dry all wounds with absorbent cotton and plug those
that continue to drain. Punctured eyes should be pressed
lightly and wiped as dry as possible. Plug the throat of
every bird, however small, to prevent drainage of stomach
contents and juices. With larger birds it is frequently de-
sirable to plug the internal nostrils also.
The specimen is now slipped beak foremost into a paper
cornucopia, care being taken that the head is not doubled
back upon the body in the process. The larger specimens
should, of course, be placed in the bottom of the collecting
bag or basket to avoid undue pressure on smaller birds.
Under ordinary conditions freshly collected birds will
not deteriorate appreciably until several hours after death.
If the hunt is considerably prolonged in very hot or humid
weather, however, it may be desirable to delay early putre-
faction in the field by swabbing the gullet with a small wad
of cotton saturated with carbolic acid before inserting the
absorbent throat-plug. The abdominal skin may also be
treated with carbolic acid by swabbing along the median
line after the feathers are parted, but care must be taken to
keep the feathers dry.
In rhe absence of carbolic acid a strong solution of
formalin may be applied to the gullet and injected into the
abdominal cavity with a syringe. Specimens treated by
either method can be skinned long after untreated birds
have spoiled beyond salvage. Although these techniques
are not required under normal circumstances, they are often
useful in the tropics, particularly if skinning has to be de-
layed until the second day.
KILLING WOUNDED BIRDS
A wounded bird should be caught and killed as quickly
BLAKE: P R E S E R V IN G B IR D S
as possible, for humane reasons as well as to prevent fur-
ther damage to its plumage. Under no circumstances
should it be struck on the head, since the hemorrhages that
invariably result considerably complicate the preparation
of a clean skin.
Wounded birds are best killed by compressing the sides
of the body in the areas just below and posterior to the
shoulder joints. Pressure thus applied immediately retards
the heart and lung action, resulting in death within a few
seconds. Small birds (up to the size of a crow) can easily
be killed in this manner with one hand, but it may be nec-
essary to kneel on very large specimens after first elevat-
ing the wings above the back.
Caution: Precautions against injury should be taken
when approaching and handling certain wounded birds.
Owls and birds of prey fight defensively with their claws
and a:^ capable of inflicting painful wounds unless firmly
grasped by the legs. Herons and various other birds peck
viciously, with special attention to the face and eyes, and
the wing-spurs of screamers and certain plovers require a
cautious approach.
LABELING AND CATALOGUING
The importance of labeling all specimens properly in
the field can not be too strongly emphasized. Unlabeled
specimens are without value for present-day research pur-
poses, and those with incomplete data are often of limited
use. Since a label with complete and accurate data is an
essential part of each specimen there must be no laxity in
its preparation.
Standard museum labels should be used whenever avail-
able. Otherwise cut labels (about 3 x 3/4 in.) from durable
white paper. This paper should be fairly water-resistant
and capable of taking ink. One end of each label is strung
on a strong thread passed through two small holes punched
about 1/4 inch from its edge. Make a knot approximately
1/2 inch from the label so that it can be examined readily
when tied to the specimen. Neat holes may be made with a
hand drill in a pile of labels held by a clamp.
10
FIELDIANA: TECHNIQUE, NO. 7
Write all data in waterproof ink, with the threaded end
of the label always to the left, so that both sides may be
read with equal ease. The face of each label should re-
cord at least the date, locality, and sex of the specimen to
which it is attached. The collector's name is also desir-
able, as are the age of the bird (as determined by dissec-
tion) and the condition of its gonads (sex organs). Write or
print legibly, indicating the month by the first three letters
(never by Arabic or Roman numerals). The locality should
be represented by three elements, i.e., the country, state
or department, and specific locality. Reserve sufficient
space for the scientific name of the specimen, this detail
being best added at the museum. Much of the primary data
(except age and sex) can be recorded before the specimen
is skinned, and the remainder added as it is revealed by
dissection.
Less essential data should be written on the back of
the label. Colors of all soft parts (eyes, beak, bare skin
of the head, legs, etc.) in fresh specimens are important
and can be recorded in concise terms. The wing spread of
large birds is often of interest and the altitude at which the
specimen was collected should be noted if known. The
latter information is especially important in mountainous
regions.
General observations and supplementary information re-
lating to the specimen (or species) and its surroundings
should be noted in a small journal or field catalogue after
a number corresponding with that of the label. Precise
identification is not necessary at this time, but each bird
should be identified by a common or descriptive name
("large woodpecker,' 1 "yellow-headed parrot,' 1 etc.).
The potential value of such a record is incalculable,
being limited only by the collector's interests and powers
of observation. Life-history notes, behavior, song, local
status or relative abundance, nest and eggs, habitat prefer-
ences, food, native names and countless similar subjects
justify investigation, and should be recorded in as much
detail as possible. An ecological description of each
collecting locality is especially desirable. Various other
matters of interest and importance will occur to the col-
lector in the field,
BLAKE: PRESERVING BIRDS
1 1
PREPARATION FOR SKINNING
Skinning birds under field conditions is at best a time-
consuming and tedious process, so it is always desirable
to arrange the work board or table, tools and materials
carefully with attention to convenience, comfort, and good
illumination. Cover the skinning surface with a clean
piece of paper (to be replaced whenever soiled) and arrange
essential tools (scalpel, scissors, forceps, threaded needle,
etc.), the corn meal and arsenic (or borax) containers, cot-
ton batting, cup of clean water, grease solvent, labels,
notebook, etc., around the perimeter, but within easy reach.
Consistency in returning each item to its original position
directly after using saves much time otherwise lost in
searching for misplaced objects.
Whenever possible, skinning should be delayed until the
blood has coagulated. The presence of rigor mortis, which
occurs in birds within an hour after death, determines the
time vhen the specimen can be skinned with least danger
of soiling by body fluids. Just before the bird is to be
skinned, replace the throat plug with a fresh piece of ab-
sorbent cotton. With large birds, particularly fish and fruit
eaters, it is often desirable to plug the vent with cotton
also.
If the eyes have been punctured remove them entirely
with sharp-pointed forceps, wipe the lids dry and insert
absorbent cotton into the empty sockets. Dried blood
stains and mud should now be removed with a stiff brush,
an old tooth brush being ideal for this purpose. If the
specimen is so badly soiled as to require washing, it is
best to wait until the skin has been removed from the body.
In order to facilitate the handling of the specimen while
it is being skinned, it is necessary to relax the appendages
at the shoulder and "knee" joints. Grasp the upper wing
bones (humeri) in each hand and force them upward and
backward as far as possible in order to stretch the liga-
ments of the shoulders. Now lay the bird on its back and
force the tibias ("drumsticks") forward and slightly out-
ward in order to relax the "knee" joints. In both processes
it is advisable to avoid breaking any of the bones, since
it is desired at this stage merely to stretch the muscles
and tendons.
1 2
FIELDIANA: TECHNIQUE NO. 7
SKINNING THE BIRD
1. Lay the relaxed bird on its back with its head to the
left (reverse all directions if left-handed) and pointing
slightly away from the operator. Bare the median line of
the abdomen with fingers of the left hand - the process may
be assisted by blowing on the feathers - and with a sharp
scalpel make a longitudinal cut from the lower part of the
breastbone to the vent. Only the abdominal skin should be
Fig. 1. Press the "knee" forward and upward into view after separating
the skin from the body along one side of the abdominal cut. Disarticulate the
legs at this joint.
penetrated, but perforations of the abdominal wall can
be plugged with cotton.
2. Sprinkle corn meal 2 along the cut and, with the butt
of the scalpel, separate the skin along one side of the cut
from the abdominal muscles below. When sufficient skin
has been freed, hold it between the thumb and the fore-
finger of the left hand and continue, in the same manner,
separating it from the side of the body until the "knee" is
exposed (Fig. 1). Sprinkle corn meal on the exposed parts
whenever necessary to prevent feathers from sticking to
the moist flesh.
3. Cut the leg free at the "knee" (femoral-tibial joint)
and complete the separation of the skin along one side of
J The illustrations accompanying these directions for making museum
specimens were made by the veteran artist and taxidermist, Leon L. Pray.
2 Fine sawdust, sand or other granular material that does not become pasty
when wet may be used instead of corn meal.
BLAKE: PRESERVING BIRDS
13
the body for the full extent of the abdominal cut. This is
best accomplished with the fingers and/or butt of a scal-
pel. Stretching of the skin and tears will be avoided if the
finger position is changed at intervals so that it will be as
close as possible to the line marking the contact of skin
and flesh.
In large birds, disarticulation of the legs requires the
use of scalpel, scissors or bone shears. With smaller birds
(up to the size of a jay) merely break the upper end of the
tibia just below the joint ("knee"), force the jagged bone
through the leg muscles to strip off the flesh and cut the
latter free from the lower end of the tibia.
Caution: Never tug or pull strongly at any portion of
the skin. Speed and efficiency in skinning largely depend
upon proper use of the fingertips and fingernails where the
Fig. 2. Cut through the lower end of the backbone and tissues at the base
of the tail after disarticulating both legs at the "knee."
14
F I E L D I A N A : TECHNIQUE NO. "
skin and flesh meet. Usually the small muscles attached
to the skin locally may be pinched apart with the finger-
nails; in fact, few stages in the skinning of most birds re-
quire the use of scalpel blade or scissors at all. Penguins,
cormorants, ducks and certain other water birds are excep-
tions in that the skin clings to the flesh more strongly than
with most birdskins.
Fig. 3. After separating the tail, grip the lower end of the back with
Creeps f o: fingers) and strip the skin forward to the shoulders by turning it
inside out.
-.. Repeat the previous process on the other side of the
Dird.
5. To separate the tail from the body, rest the uropyg-
ium (identified as a lump at the base of the tail feathers)
on the left forefinger and hold it in position with the thumb.
Now raise the forefinger slightly to expose the tissues and
cut across the region of the vent, including the vertebral
column, thereby freeing the tail (and uropygium) from the
body. A scalpel may be usee, but the danger of cutting the
skin -and one's forefinger below -is best avoided by the
use of scissors. In the latter technique, merely rest the
BLAKE: PRESERVING BIRDS
15
rounded side of the blunt blade on the skin and cut across
the tissues and vertebrae as with the scalpel, the depth of
the cut being easily judged by pressure of the scissors on
the left forefinger below (Fig. 2). If the body cavity has
been penetrated, with consequent exposure of intestines,
replace the latter and plug the opening with cotton.
6. Raise the specimen somewhat above the table by
gripping the end of the severed backbone with forceps
(Fig. 3). Then carefully strip the skin toward the fore part
of the body, using the fingers of the free hand. 1 When turn-
Fig. 4. Expose the shoulders and lower neck before cutting the wings free
at the shoulder joints.
ing the skin inside out during this process avoid pulling or
stretching it unduly. The action is rather that of applying
pressure with the fingertips and nails along the line at
which the skin and body are joined. The scalpel will be
needed only occasionally. Work methodically around the
Large birds may be rested on the table throughout the skinning process
and both hands used in removing the skin. Sometimes it is convenient to sus-
pend such specimens above the table by means of a swinging hook inserted
into the lower pelvic region, being careful to avoid injury to the gonads
within.
16
FIELDIANA: TECHNIQUE NO. 7
body and apply corn meal generously on all exposed skin
and flesh surfaces as needed. When the rump or pelvic
region is sufficiently exposed, the forceps may be dis-
carded in favor of either hand as the skin is reversed to the
shoulder joints (Fig. 4).
7. Cut both wings free at the shoulder joints with
scissors or scalpel and turn the skin back to the base of
the skull.
8. Rest the bird on the table (ventral side down and
facing away from your side) and carefully manipulate the
neck skin over the back of the skull with the thumbs and
fingers. Special care must be observed in clearing the
base of the lower mandibles of some birds (grosbeaks,
etc.), but the butt of a scalpel may be used advantageously
as a lever on macaws, toucans and other large birds. It is
important - as in skinning the body - to work methodically
Fig. 5. Manipulate the skin over the skull and cut the ears free at the
point where they insert into the skull.
around the skull as you progress forward. Cut or pinch
apart the small muscles attached to the skin whenever
necessary. The ears will be recognized as membranous
tissue inserted into each side of the skull behind the eyes
and just above the base of the mandibles (Fig. 5). The
ears must be pinched free or cut with a scalpel before be-
ing skinned forward to the eyes.
Most ducks and many woodpeckers have necks too small
to permit passage of the skull. With these it is necessary
BLAKE: PRESERVING BIRDS
17
to sever the neck near the base of the skull and skin the
head (as instructed below) through a cut in the scalp ex-
tending from the crown to the neck stub. With hornbills,
guinea fowl and various birds having casques or other hard
structures on the crown, the procedure is the same except
that the cut is made in the throat (Fig. 6). In either case
sew the cut together neatly after the skull has been cleaned
and poisoned and the skin reversed.
9. Cut across the exposed transparent membrane over
the eye, being very careful to avoid cutting the lids and
Fig. 6. The heads of birds having very small necks or hard outgrowths
on the skull must be skinned through a cut in the throat or the crown.
eyes themselves. The membranes are easily pinched free,
but it is preferable to cut them cleanly with a scalpel while
they are stretched taut with the left thumb and forefinger.
Reverse the scalpel and scoop out each eye with the butt;
then skin forward to the very base of the mandibles. With
owls it is not desirable to remove the eyeballs, which are
rigidly fixed. Rupture the eyes with a sharp instrument,
clean out the contents without soiling the plumage, and
continue as with other birds.
10. To remove the base of the skull and brain make
four clean cuts with scissors as shown in Figure 7. First
18
F IE I. DIANA: TECHNIQUE NO. 7
Fig. 7. Make four deep cuts in the skull to free the neck and expose
the brain.
cut across the roof of the mouth from below (No. 1) without
injuring the rami or lower mandibles. Then make a deep
incision from each end of the preceding transverse cut rear-
ward (parallel to, but within the branches of the mandibles)
to a point on the back of the skull somewhat above the
base of the neck (Nos. 2 and 3). A fourth cut (No. 4) con-
necting the posterior ends of the preceding incisions
serves to disengage the neck and its attachments from the
Fig. 8. Manipulate the skin over the exposed skull after removing all soft
parts (eyes, brain and muscles') and applying a preservative.
BLAKE: PRESERVING BIRDS 19
skull. Put the body aside for sexing, and to serve as a
model for the preparation of a cotton substitute. Fragments
of the brain not drawn forth cleanly as the neck is removed
should now be picked out with forceps, and the larger
muscles of the skull and lower jaws clipped away.
11. When the skull has been cleaned (avoid disarticu-
lating the lower mandibles) and all fragments of muscle cut
or stripped from the skin of the neck and head, poison
these parts thoroughly with powdered arsenic (or borax).
Examine the condition of the skull - whether the roof of the
braincase appears granulated or clear - for an indication of
the bird's age and record the results (see p. 23 for detailed
explanation). Now turn the neck right side out. 1 If the
neck has dried and shrunk from exposure it should be
moistened until pliable before being manipulated over the
skull (Fig. 8). When speed in skinning has been achieved
it is desirable to leave the skull exposed until the entire
bird has been cleaned and poisoned, and the dorsal feather
tracts are sewed.
12. Feathers of the head that have been disarranged
while turning the skin may now be smoothed by inserting
the tips of the forceps through the eye and stroking the
flesh side of the skin of the crown and cheeks (Fig. 9).
13. Working backward from the fore part of the speci-
men, methodically remove all shreds of flesh still clinging
to the skin. Invert the wings to the first ("elbow") joint
and cut away all muscles of the humeri (upper wing bones).
Now skin the wings out to the "wrists" (carpo-metacarpal
joints), leaving the secondaries attached, and remove the
radius (uppermost of the two bones in this area) and all
associated muscles with scissors. These parts, including
the radius, may be pinched away in small birds.
With tinamou, ducks and most large birds it is usually
advisable to skin the wings only so far as the first, or
"elbow" joint, and thereafter remove the muscles of the
next section ("forearm") through a cut made along the
The empty eyeballs of owls should be packed with cotton "eyes," smooth
side outermost, before reversing the skin. Eye plugs may also be inserted
into the sockets of other birds at this time, but it is preferable to do so after
the skin has been cleaned and turned feather side out.
20
FIELDIANA: TECHNIQUE NO. 7
under side of the wing (Fig. 10). Poison all exposed parts
thoroughly and stitch the cut together. Finally, expose and
scrape away the small area of flesh on the under side of
the outermost or "wrist" joint and probe arsenic or borax
into all parts of the cavity. 1
14. Skin the legs down to the first joint and shear off
all flesh without removing the bones. Now turn the skin
right side out after poisoning both the skin and the bones.
Leg muscles of birds the size of a crow or larger should be
partially replaced with tow or cotton. Disarranged feath-
Fig. 9. Insert the tips of the forceps through the eye and smooth the
feathers of the crown and cheeks by stroking the flesh side.
ers of the thighs can be smoothed by firmly stroking the
legs downward.
15. The leg tendons of many medium-sized, and all
large birds (including waterbirds, hawks and owls, etc.)
This precaution is very important for all large birds, particularly ea-
gles. An oversight in this matter can easily cause the loss of important
wing-feathers.
BLAKE: PRESERVING BIRDS
21
must be removed to prevent decay. Make a deep cut in the
sole of each foot, insert the points of strong forceps or
probe beneath the tendons thus exposed (Fig. 11) and pull
firmly to extract the ends previously severed while clean-
ing the upper leg bones. Pack arsenic or borax into the
Fig. 10. In large birds
remove the muscles
of the "forearm" and
wrist" through a
cut made beneath
the wing.
tendon canals with a probe. Tendons must also be removed
from beneath the toes of birds having particularly large or
fleshy feet. In large herons, or birds having very fleshy
legs, it is important also to slit the skin on the inner side
of the "heel" or tarso-metatarsal joint so that the joint it-
self, and all adjacent parts, can be poisoned. Always err
Fig. 11. Draw the tendons from the lower legs (tarsi) of all large birds. It
may also be necessary to make a cut on the inner side of the "knee" joint,
and remove the tendons beneath the toes.
on the side of safety when in doubt as to whether the legs
and feet require special treatment.
16. Pry the skin away from the base of the tail to ex-
pose the oil glands that lie just above the uropygium; then
22
FIELDIANA: TECHNIQUE NO. 7
scrape or cut out the contents. This oil must be removed
entirely, and the parts thoroughly poisoned, to prevent sub-
sequent loss of tail-feathers. Now trim the uropygium care-
fully with scissors to remove all surplus flesh and bones,
but leave sufficient tissue to support the tail-feathers.
DETERMINATION OF SEX
The sex of each specimen should be determined by dis-
section even when dealing with adult birds of species in
which the males and females have distinct plumages. After
the skin has been removed lay the body on its back and
carefully cut through the left side of the abdominal wall
from the vent to a point just beyond the forward edge of the
left thigh. Press aside the left thigh and mass of intes-
tines to expose the sex organs (gonads) that lie close to
the backbone at the forward end of the kidneys (Fig. 12).
The testes, or male organs, will be recognised as a pair
of rounded or somewhat ovoid bodies. They are usually
white or yellow, but may be very dark in color. These
organs vary a great deal in sise, depending upon the sea-
Fig. 12. Position and appearance of the sex organs
(male, left; female, right).
son of the year. In immature birds, or during periods of
sexual inactivity, the testes may be confused with the
adrenal bodies, which are present in both sexes. The
adrenal bodies, however, are smaller and flatter, are either
BLAKE: PRESERVING BIRDS 23
yellow or orange in color, and are located farther forward
within the anterior border of the kidneys.
The female organs lie just to the left of the median
plane and usually consist of a single ovary, although a
vestige of the right ovary may also be present. The latter
is sufficiently uncommon to justify a comment in the field
catalogue when found. During periods of sexual inactivity
the ovary resembles an irregular mass of minute granules
not readily confused with testes. During the breeding sea-
son the developing eggs are easily recognized, as is the
oviduct, a membranous, whitish tube leading from the ovary
down the left side to the vent. A small magnifying glass
will be found useful in identifying the organs of either sex
when the gonads are not enlarged.
The male sex is indicated by the spear and shield of
Mars (<5), whereas the mirror of Venus (?) is used as the
sign of the female. If the sex is undetermined by dissec-
tion the fact should be expressed on the label by an inter-
rogation mark (?). Never guess the sex of a specimen or
make a determination on the basis of plumage alone. The
condition of the sex organs, as determined by dissection,
should be indicated as follows: 1
"t.e." = testes enlarged, when the increased size would
indicate that breeding was under way.
"t.n.e." : testes not enlarged, when there is no possi-
bility that the bird is in condition to breed.
Intermediate conditions may be indicated by "t.so.e.
(itestes somewhat enlarged) and "t.sl.e." (stestes slightly
enlarged). Corresponding conditions of the ovary would be
written "o.e.," "o.n.e.," and so on.
Any inequality in the size of the male organs, the pres-
ence of a right ovary, or any other abnormality in the re-
productive organs is worthy of special note.
DETERMINATION OF AGE
In most passerine birds ("song-birds" and their allies)
the condition of the skull gives a definite indication of the
1 Copied from James P. Chapin, The Preparation of Birds for Study, 1940,
in the interest of standardization.
24 FIELDIANA: TECHNIQUE NO. 7
age of the bird that is not always apparent in its plumage.
In nestlings and very young birds the roof of the braincase
consists of a single sheet of bone that appears translucent
and clear when held up to the light. In adults the brain-
case is formed by two layers of bone separated by air
spaces that appear more opaque and granular.
The clear area of the roof of the braincase in nestlings
is gradually reduced with age, but persists until about the
third month. It is usually lost after six months, the skulls
of most passerine species then being completely ossified
and appearing somewhat speckled when held before a light.
The condition of the skull (passerine species only)
should be noted when the brain is removed, and the infor-
mation written on the label as "sk.n.o." (skull not ossi-
fied) or "sk.o." (skull ossified) as the case may be.
CLEANING AND DECREASING
Soiled plumage must be cleansed of all foreign matter
and the skin degreased (if necessary) before it is made into
a study specimen. Dried blood and mud often respond to a
stiff brush, but, if badly soiled, the affected areas must be
alternately swabbed with cotton that is saturated with
water and brushed dry with corn meal. Heavy magnesium
oxide powder, used alone or with corn meal (50 per cent by
bulk), is a very effective absorbent and hastens the work
of restoring the normal texture of the dry plumage. Fine
sawdust, dry sand and similar substances may also be
used, but they are much less absorbent than corn meal.
If very badly soiled, the entire skin may be carefully
washed in clear water (preferably warm) several times be-
fore being dried, but this is rarely necessary. When it is
finally cleansed, and the plumage fluffed into dryness,
shake out all remnants of the absorbent material.
Fat and grease stains, which cannot be dissolved by
water, must be removed by other means. The skins of
ducks, cormorants and various other water birds require
special attention, since the flesh side is usually blan-
keted with fat that must be removed entirely. Methodically
scrape these skins from the tail forward with a dull knife
and rub off every bit of fat with corn meal. Fatty areas
BLAKE: PRESERVING BIRDS
25
between the feather butts may be cut out with small scis-
sors or scraped away with a -arire orush. A spoon having
serrations filed along one side is often useful. Quantities
of oil may also be absorbed rapic : applying corn meal
or a similar absorbent that has first been heated.
Various solvents (white gasoline, benzine, naphthalene)
may be used in removing grease stains from birdskins.
Carbon tetrachloride is perhaps best of all, since it is
quite safe to handle and is also extremely effective as a
solvent.
Apply the solvent liberally on all greasy areas with a
cotton swab, or submerge the entire skin in the solution if
the bird is badly soiled. The plumage is then dried with a
brush and corn meal (or magnesium oxide) as descrizei
above, and all particles of the absorbent finally shaken or
blown out.
The steins of ducks, geese and various other water
birds are often excessively greasy, and are best cleaned
under laboratory conditions whenever possible. In temre:-
ate latitudes these may be well salted, packed separately
from other skins, and shipped home for final treatment even
months later. In the tropics birdskins must never be treat-
ed with salt, as the moisture that forms will cause the
skin to disintegrate rapidly.
POISONING THE SPECIMEN
ir. en the specimen is thoroughly cleaned and degreased,
poison the flesh side and all bones generously with pow-
dered arsenic or borax. If the skin has dried out in sr
it must be moistened to secure penetration of the arsenic
or borax.
The skin, which has been well cleansed by wash::.,
or by dipping in a solvent, must be completely repoisoned;
otherwise merely dust it with preser s and make cer-
tain that the wings, the legs and the base of the tail are
well protected.
MAKING A STUDY SKIN
1. Two parallel strips of roughened skin near the
median line of the back mark the dorsal feather tracts
2 6
FIELDIANA: TECHNIQUE NO. 7
(Fig. 13). With needle and thread take a stitch through
each of these near their upper ends and draw them some-
what closer (but not entirely) together. 1 Birds the size of
a crow or larger should have a second stitch across the
lower ends of the tracts. In very large specimens the
upper wing bones (humeri) may also be tied together in
parallel position as a means of further supporting the wings
of the completed skin.
2. Twirl a small piece of cotton (held with forceps)
between the fingers of the left hand as shown in Figure 14,
Fig. 13. Stitch the dorsal feather tracts loosely together after the skin
has been cleaned and thoroughly poisoned.
to form an eyeball. Now raise the specimen by its beak
and insert the artificial eye into its socket by way of the
neck and base of the skull. Withdraw the forceps and flat-
ten the eye somewhat with the thumb to prevent its protrud-
ing as the skin shrinks in drying. Finally, carefully shape
the lids around the eye with forceps.
3. Insert the other eye in the same manner and place
the skin on its back with the abdominal cut widely sepa-
rated. The upper wing bones (humeri) should now be lying
parallel against the skin of the back.
The distance left between the feather tracts after stitching varies with
the size of the bird, but is roughly one half the width of the inter-tract area
before stitching.
BLAKE: PRESERVING BIRDS
27
4. To make an artificial body first obtain a straight
smooth twig 1 long enough to reach from the throat to the
abdomen. With a thin strip of cotton held in the left hand
wrap a smooth layer around the greater extent of the twig
by twirling it between the fingers of the right hand. Tow
may be used for large birds. Now, with the same strip of
cotton (or tow) bind an inch or so of the tip (first mois-
tened to prevent slipping) of a long slender "spindle" 2
Fig. 14. Artificial eyes can be
shaped from a bit of cotton held in the
left hand and rotated on the points of
forceps.
as tightly as possible against the bare end of the twig as
shown in Figure 15.
Continue rotating the "spindle" (or over-length twig, as
the case may be) with the right hand and wrap cotton along
its shaft to a point marking the specimen's length from
throat to base of tail. Still using thin, smooth strips of
cotton, gradually build up the covered portion of the twig
and "spindle" to form the neck and body. Shape these in
the palm of the left hand as cotton strips are added to pro-
duce a manikin having a smooth surface, and about the size
The round, wooden "applicators" used by the medical profession are
ideal for small to medium-sized birds. Straight wire of suitable length is
fairly satisfactory.
Many collectors dispense with a "spindle" entirely and merely wind the
artificial neck and body about a straight twig or stick sufficiently long to ex-
tend from the throat to the tip of the tail, or just beyond. In either case, the
"spindle" or over-length twig is a convenience for holding the specimen be-
fore the skin has dried, without disturbing its plumage by unnecessary
handling.
28
FIELDIANA: TECHNIQUE NO. 7
and shape of the original. If the artificial body is loosely
wound it should be made somewhat larger than the original
body.
5. Insert the pointed end of the artificial neck well up
into the throat of the specimen (not into the cranial cav-
ity) 1 and carefully manipulate the skin over the cotton
body or manikin by working methodically from the head
backward towards the tail. The process may be simplified
|« mn i i iii ninm i nrinin Mnnrnjfr
Fig. 15. An artificial cotton (or tow) body for small to medium-sized birds
is prepared by means of the "spindle" technique.
after inserting the neck if the specimen is held upright by
means of the "spindle" while working the skin over the
manikin with the free hand.
It is important that the upper wing bones remain well up
on the back where they normally are held in position by the
stitch connecting the dorsal feather tracts. Should this
stitch tear loose it will be necessary to remove the body
and re-stitch the feather tracts before continuing. If the
skin is found to fit too loosely, strips of cotton may be
needed. Padding for the throat and neck, when required, is
best inserted through the open beak.
6. Replace the specimen on the table, on its back,
and sew the abdominal cut loosely together with a heavily
Owls are exceptions. With these birds it is best to press the sharpened
end of the neck stick or wire firmly into the cranial bones at the base of the
upper mandible in order to clinch the head in its normal position.
BLAKE: P R E S E R V IN G B IR D S
29
knotted thread (Fig. 16). Stitching is done on alternate
sides of the cut, from the flesh side outward, beginning
near the forward end of the cut and working back to the
tail. The latter should be anchored firmly to the body by
means of a stitch or two taken through the uropygium or
remnants of the anal ring before cutting the thread. This
additional support is very desirable in birds having long
tails.
7. Close the beak with a bit of moistened cotton
wrapped about the mandibles, or pass a threaded needle
Fig. 16. With the artificial body in position, the first stitch is made in the
abdominal incision. The protruding "spindle" is convenient in handling the
fresh specimen and is later withdrawn.
through the nostrils and draw the beak together by means
of a loop tied beneath the lower mandible. Avoid injury to
structures of the external nostrils. If the bird has an ex-
tremely conical beak it may be necessary to press a pin
through the skin of the chin (near the juncture of the rami)
into the palate.
8. Cross the feet beneath the abdomen with toes fac-
ing inward and tie the label firmly to the legs at their point
of contact.
30
FIELDIANA: TECHNIQUE NO. 7
9. Place a smooth, thin layer of cotton 1 on the table
for use in wrapping about the specimen until the wings and
plumage have dried in position. The cotton should be
Fig. 17. Withdraw the
"spindle" by a counterclock-
wise movement before wrapping
the finished specimen for drying
roughly rectangular in shape and sufficiently large to en-
close and protect the entire bird.
10. The specimen may now be lifted and handled freely
by the "spindle" as the plumage is arranged with the free
hand. Extend each wing in turn to see that all feathers
are in proper position as the wings are folded, and that the
Large birds may be wrapped in cheesecloth or paper. In the absence of
suitable cotton the completed study skin may be slipped into a paper cylinder
or cornucopia. This practice is not recommended, since the specimen is still
pliable, and hence easily distorted.
BLAKE: P R E S E R V IN G B IR D S 31
tips of the folded wings are evenly aligned above the tail.
Contour feathers of the neck and body that have been dis-
turbed should now be lifted and arranged with slender
forceps.
WRAPPING AND DRYING BIRDSKINS
When the plumage has been arranged as in life lay the
specimen, back downward, in the cupped palm of the left
hand and withdraw the "spindle" by rotating it in a coun-
terclockwise direction (Fig. 17). If the body has been
wound on a long twig or stick, rather than on a removable
'spindle, " merely break the twig as close as possible to
the abdomen. Now grip the specimen at the wing level with
the right hand and place it on the cotton sheet set aside
for wrapping.
Methods of wrapping fresh specimens vary and can only
be mastered with practice. Two corners of the cotton sheet
may be brought across the bird so that they overlap on the
throat and breast, and the body and wings lightly bound in
position by folding over the sides. Otherwise the specimen
may be placed across one corner of the sheet and carefully
rolled into its wrapping. If the latter method is used, avoid
distorting the specimen by uneven pressure in wrapping.
Finally, spread the tail-feathers slightly, check the posi-
tion of the wings and feet once more, and put the specimen
aside for drying. 1
Freshly prepared specimens should be dried as rapidly
as possible without actually baking the skins. Ordinarily
there is no difficulty in temperate climates, but special
methods are often necessary in humid tropical areas, par-
ticularly during the rainy season.
Never dry skins under direct tropical sunshine except
for short intervals, or pack undried specimens in an airtight
container. Free circulation of dry air permits even, gradual
drying. These conditions can often be met by hanging
Each bird should be rewrapped on the second day when it is still pliable,
but sufficiently dry to permit handling without distortion. Defects overlooked
on the first day can often be corrected very easily at this time, before the
specimen is thoroughly dry.
32 FIELDIANA: T E CH N IQ U E , N O . 7
shelves suitably protected from insects, mice, etc. 1 During
the rainy season, or in very humid areas, it may be neces-
sary to place the specimens near a fire (but away from
smoke), or arrange suitable conditions by means of several
lanterns placed with the skins in a small tent. When col-
lecting in dense tropical jungles the area cleared of brush
and trees for the camp site usually affords adequate condi-
tions for drying specimens.
A specially constructed drying box is of utmost con-
venience when traveling, or for any serious expeditionary
work. The best type is of sturdy, crate-like construction
with a solid bottom but with the sides and top of fine, rust-
proof, wire netting. This box or crate should be fitted with
a series of light trays having bottoms of wire netting and
sides of various depths (1-1/2, 2-1/2, and 4 in.) to accom-
modate specimens of all sizes. A slipover cover of heavy
canvas gives adequate protection to the contents under
ordinary conditions. For very rugged field conditions dry-
ing trays of the same type are best housed in a small trunk
or hinged box that has solid sides.
PREPARING LARGE BIRDSKINS
The foregoing instructions for preparing birdskins apply
particularly to small and medium-sized species. Consider-
ably larger birds can also be treated in the same manner,
but ordinarily they are dealt with otherwise after they have
been skinned and processed.
Very large birds can not be conveniently handled by
means of a "spindle," nor is that method desirable since it
requires quantities of special cotton or tow. In all large
species having ordinary proportions (eagle, turkey, etc.),
the artificial neck and body should be made with straw,
wood "excelsior" or similar substance bound firmly with
string around a straight stick of suitable length. This arti-
ficial body should be somewhat smaller than the original,
but of approximately the same proportions. Place the mani-
kin within the skin as with small birds, insert padding
locally as required, and sew up the abdominal cut. Cheese-
Naphthalene flakes are a mold and insect repellent and should be sprin-
kled in the drying trays or on the specimens whenever they are exposed.
BLAKE: PRESERVING BIRDS
33
cloth, paper, or strips of cotton can be used to wrap large
specimens for drying.
Large birds having very long necks or legs (flamingoes,
herons, swans, geese, etc.) are handled in much the same
manner except that the core of the manikin must be made of
wire rather than wood. With these and similar birds it is
necessary to bend the neck wire after it has been inserted
so that the head extends alongside one wing, in order to
meet storage specifications. Similarly, the legs (tarsi) of
herons, flamingoes, storks, etc. must be bent beneath the
Fig. 18. Special methods in packing are recommended for species having
long necks and legs, or elaborate crown adornments.
body. The over-all length of a specimen should not exceed
3 feet. The special "make" of skins required for these
and certain other birds is illustrated in Figure 18.
If circumstances prevent the preparation of finished
specimens in the field, the skins of larger species may be
shipped as "flats" for further attention in the laboratory.
In this event, after the bird has been skinned, degreased
and poisoned as usual, merely place sufficient loose straw,
excelsior or tow within the specimen to permit free circula-
tion of air. A suitable label must, of course, be attached.
The method is not recommended for small birds, and should
not be used at all except as a last resort.
34
FIELDIANA: TECHNIQUE, NO. 7
Ostriches, rheas and similar large, flightless birds are
exceptions, since they can be prepared only as "flats" in
the field. After skinning these birds it is necessary to cut
the inner side of the lower legs (tarsi) for their full length
in order to separate the skin and bones. Skin the toes com-
pletely through cuts on the under side and remove the ten-
dons without disarticulating the joints. In a dry climate
the skin should be thoroughly salted. A mixture of one
part salt to three parts alum is preferable in humid regions.
Distribute grass, leaves, etc. loosely within the skin to
keep all parts separate, and dry the specimen before
packing.
DEVELOPING SPEED AND EFFICIENCY
There should be no attempt to develop speed until every
step in the preparation of specimens is fully mastered and
has become second nature. Superior birdskins with com-
plete data are the first consideration, and these standards
must never be lowered in the interest of speed.
Nevertheless, increased efficiency in the preparation
of specimens is a matter of importance in the field, since
every hour spent at the skinning table is an hour lost from
more important activities. The beginner usually finds that
each of his first specimens requires an hour or more of
tedious work, leading to very disappointing results. With
continued practice there should be marked improvement in
later specimens, and the time spent on each will have been
reduced to half an hour or so.
When a point has finally been reached beyond which the
specimen is not improved nor the time for its preparation
reduced, the collector should consider his work-habits crit-
ically for evidence of inefficiency. It is usually possible
to increase speed considerably by attention to the follow-
ing details.
1. Maintain an orderly work-table, with only the nec-
essary tools and materials at hand, and with each item
assigned to a specific position. Experience will indicate
the instruments needed, and the order in which they should
be placed.
BLAKE: PRESERVING BIRDS 35
2. Return each instrument to its original position im-
mediately after using it. With practice the tools can be
picked up almost without looking at them, and minutes can
thus be saved in the aggregate on each specimen.
3. Avoid uncertain or fumbling movements. In so far
as possible, think ahead to the next operation and the tool
required. Do not, for example, reach for scissors to dis-
articulate the tail, and decide belatedly that the forceps
are first needed for quite another purpose.
4. Avoid lifting or handling the specimen unneces-
sarily - a common failing with all beginners. When the bird
must be picked up, do so only with a specific objective in
mind.
5. Finally, maximum efficiency in the preparation of
birdskins - that which results in production of five, or even
more, average-sized specimens per hour - can be achieved
only by conscious effort. When practicing to increase
speed it is helpful to work with a watch in view and time
every operation. Try to reduce each by seconds in later
specimens, being careful, of course, to maintain high
standards of workmanship.
PACKING BIRDSKINS FOR SHIPMENT
Birdskins must be thoroughly dry before they are packed
permanently. Whenever possible expose the dried skins
to direct sunshine or other heat for a short period directly
before packing them so that remaining moisture will be re-
duced to a minimum. The individual skins, still enclosed
in their wrappers, are then packed side by side and layer
upon layer, in a strong box that is at least moderately air-
tight and waterproof. These conditions may be approxi-
mated by lining the container with waxed paper.
Pack specimens of approximately equal size together
whenever possible; in any event, avoid placing unprotected
small birds among very large specimens. Heavy objects,
skeletons, and salted skins must never be packed in the
same container with study skins. Pad all beaks with cot-
ton or other soft material and allow for sufficient clearance
between the tips of the tails and the end of the container.
Sprinkle naphthalene flakes among the specimens as pack-
36
FIELDIANA: TECHNIQUE, NO. 7
ing progresses and fit each bird into the contours of adja-
cent specimens to reduce the possibility of movement in
transit. Birdskins can withstand considerable pressure
that is evenly distributed, but they are soon distorted if
loosely packed.
PRESERVING SPECIMENS FOR ANATOMICAL STUDIES
Both skeletons and entire birds preserved in fluid are
desirable, but these usually should not be collected until a
satisfactory series of study skins of the species has been
o btained.
Leave intact the bones of birds selected for preserva-
tion as skeletons. Such specimens are merely "roughed
out" in the field, since laboratory technicians are better
able to prepare the finished skeleton. With these birds it
is sufficient to tear off the skin and remove the larger
muscles of the wings, legs and breast, and all internal
organs. The tail- and large wing-feathers may be clipped
short for convenience. Avoid injury to various small or
obscure bones of the throat, wing-tips, region of the vent
and elsewhere. These are no less important than major
skeletal parts. The windpipe should not be disturbed,
particularly in ducks, nor the brain in small birds. Care-
fully disarticulate the heads of large birds where the first
vertebra joins the skull and remove most of the brain by
way of the foramen with a looped wire. Pierce the eyeballs
and press out the fluids. In removing the viscera be sure
to determine the sex, and record all other essential data on
a durable label attached to a large bone. Correct identifi-
cation of the specimen will be assured either by making a
cross-reference to a skin of the same species, or by pre-
serving the skin with a number duplicating that of the
skeleton.
If the skeleton has been properly roughed-out and dried
there should be little putrefaction. Dust all parts with
borax and fold the skeleton into a compact bundle, with the
neck and appendages bound into position with a string.
The legs ordinarily can be folded neatly into the abdominal
cavity; sometimes it may be necessary to disarticulate
thern at the hip joint before placing them there. Finally
BLAKE: P R E S E R V IN G B IR D S 37
wrap the skeleton in cheesecloth and permit it to dry thor-
oughly before it is packed for shipment. Skeletal material
is never, of course, packed with skins.
Entire birds are best preserved in 5 per cent formalin 1
or in alcohol (85 percent). The hardening action of the
forner can be reduced by adding two tablespoonsful of salt
to each quart of the solution. Alcohol becomes diluted by
the juices of fresh birds and should be changed at intervals.
Specimens can also be preserved in very strong native
spirits when necessary.
The larger muscles and all parts of the abdominal cav-
ity must be penetrated by the preserving fluids. Injections
are made with a large hypodermic syringe. Otherwise, slit
the abdomen and the larger fleshy masses so that the criti-
cal areas will be pickled. Determination of sex must await
dissection, but other critical data should be recorded on a
fluid-resisting label, either with a soft pencil or with
waterproof ink. Dry the latter thoroughly before immersing
the specimen. With small birds it is desirable to give a
cross-reference to a study skin of the same species as an
aid in identification.
Specimens that have been well pickled, as determined
by examination, may be sealed while still moistened in an
airtight container for shipment. Specimens that show soft
or discolored areas should be reinjected and placed in fresh
preservative, and re-examined before they are packed. Pack
the specimens firmly so that none will be damaged by be-
ing shaken. Numerous small birds can be wrapped together
in cheesecloth for mutual protection.
INSTRUCTIONS FOE SHIPPING
Natural history specimens collected for public mu-
seums, or intended for other bona fide scientific purposes,
may ordinarily be cleared for export very readily when local
regulations have been met. Export regulations differ some-
'Commercial formaldehyde (rformalin) is usually sold as a 40 per cent
solution. Mix one part of this with eight parts of water (by volume) to obtain
the 5 per cent solution required for the preservation of anatomical specimens.
38
FIELDIANA: TECHNIQUE, NO. 7
what in various countries and the collector is best advised
as to these by the governmental agency concerned.
Specimens forwarded to Chicago Natural History Muse-
um enter the country free of duty, customs clearance ordi-
narily being accomplished in Chicago. Small parcels, in
light wooden boxes, should be sent parcel post. Shipments
of specimens intended for this Museum should be clearly
addressed and bear, in addition, a statement of contents as
follows: "Natural History Specimens for Scientific Pur-
poses Only. No Commercial Value." Notify the Director
of the Museum by fastest post at the time of shipment,
preferably giving a list of the contents of the shipment,
and in any case stating the number of specimens sent.